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The 2016 census was termed the eCensus as it was intended to be mostly completed online, saving about $100 million. IBM, which worked with the ABS on two earlier censuses, was given the job.

The committee said concerns about privacy had been a regular feature of recent censuses and this year's event especially so as the ABS planned to retain names and addresses, initially indefinitely but finally for up to four years.

That was a significant change which warranted much more public consultation and external scrutiny.

"That level of consultation undertaken by the ABS in the lead-up to this decision was manifestly inadequate, especially considering the changes affect every Australian household," the report said.

Although concerns were expressed about security of census data, the committee concluded the risk was small, although the ABS needed to work harder to reassure the community their data was safe.

Census day started with a pair of distributed denial of service attacks (DDOS) which were repulsed. DDOS occur when malicious actors use a network of compromised computers to repeatedly seek to access and overload the census website.

A third DDOS occurred on census night and was also repulsed. But a fourth raised concerns of data leakage and IBM shut off the census, which ABS didn't reopen until the afternoon of August 11.

Despite the problems, the ABS said the census response rate was over 96 per cent, comparable with censuses in 2006 and 2011.